White blood cell (WBC) differential count is a clinical analysis that enumerates the total number of leukocytes in a per volume blood sample, and classifies the leukocyte population into different types or subpopulations, such as lymphocytes, monocytes, neutrophils, eosinophils and basophils. The analysis is useful for diagnoses of diseases such as leukemia, infections and allergies.
Presently, automated leukocyte differential counting is conducted in a hematology analyzer or in flow cytometer by utilizing differences in cell morphologies or cellular contents. The analysis of cell morphologies use detection methods such as light scattering and electrical impedance of individual cells. Alternatively, leukocytes can be analyzed based on their cellular contents, which can be selectively stained by fluorescent dyes and detected by corresponding fluoresence emissions, such as by the described reagents and methods in the disclosures of U.S. Pat. Nos. 6,197,593, 6,004,816, 5,296,378, and 5,434,081, 3,916,205.
In recent years, there is increasing interests of miniaturizing the leukocyte differential counting for newly emerging applications such as for NASA spaceflights and bedside healthcare. The previous mentioned reagents and methods for leukocyte analysis are all developed for macro-sized hematology analyzers and flow cytometers, but not optimized for miniaturization applications. For example, the previously mentioned reagents and methods for leukocyte classification either requires a combination of the light scattering detection and the fluorescence detection, or uses multiple steps of exposure and fluorescence detection, which increases system complexity and are difficult to be used in miniaturized instruments. Therefore, there still exists a need in the art for compositions and methods for leukocyte differential counting especially for miniaturization purposes.